Well just going on the novelization alone. It says she her eyes bulged and she had to stop her jaw from dropping to the floor. Then it says she did her best to act like she didn't know him.

It's the jaw dropping and eye bulging that makes me think she didn't know, but even that is not really clear because it doesn't actually say she didn't know. She could have just been surprised he showed up that day...lol. idk...hopefully at some point there will be some tie in comics or what not to clear this up.

At this point I'm inclined to agree with Krypton Inc that it's up to you how you want to interpret it. There really is no clear answer.